Radiotherapy homologous electron pair tomography imaging system and image reconstruction method

Abstract

The radiotherapy homologous positron emission tomography (P2T) imaging system and image reconstruction method of the present invention. The radiotherapy homologous P2T imaging system is provided with: a linear accelerator head; two annular detectors, the two annular detectors are located in the same axial plane and are symmetrically arranged; the linear accelerator head is placed at the notch of the double annular detectors; the annular detectors are composed of a plurality of detection modules arranged along a circle. The imaging system of the present invention avoids the damage to the detectors caused by the direct irradiation of high-energy X-rays on the detectors, and improves the clinical feasibility of the P2T imaging system. The image reconstruction method of the present invention is based on the double annular P2T imaging system, uses the Monte Carlo method to simulate the positron pair production effect generated by the irradiation of a high-energy X-ray pencil beam on human tissues and the coincidence events formed by the annihilation of positrons collected by the detection units. Attenuation, random, and scatter corrections are performed on the coincidence events, and the P2T image is quickly reconstructed by using the intersecting line method, avoiding the decrease in imaging resolution.

Description

Technical Field

[0001] The present invention relates to the field of radiotherapy imaging technology, and particularly to a double-quarter-ring radiotherapy homologous electron pair tomography imaging system and an image reconstruction method. Background Art

[0002] Online target area tracking and dose monitoring in tumor radiotherapy are crucial for improving radiotherapy accuracy, reducing the occurrence of complications, and improving the quality of life of patients. To dynamically monitor the changes in tumor position caused by physiological factors such as respiration and intestinal peristalsis during radiotherapy and be able to timely adjust the direction and dose distribution of the radiation beam to ensure accurate irradiation of the tumor tissue while minimizing damage to surrounding normal tissues, currently commonly used online tumor localization methods include kilovolt X-ray imaging, megavolt X-ray electronic portal imaging system, megavolt cone beam computed tomography (CBCT) imaging, and other structural or functional imaging tracking techniques such as online ultrasound, magnetic resonance (MR), and positron emission tomography (PET), etc. On the other hand, online dose monitoring technology monitors the radiation dose distribution received by the patient through real-time imaging and compares it with the pre-established treatment plan to timely detect and correct dose deviations, thereby ensuring that the patient receives accurate radiation dose during treatment, improving the treatment effect, and reducing adverse reactions and complications during treatment. Existing online dose monitoring devices include megavolt CBCT, electronic portal imaging system, ionizing radiation-induced acoustic imaging system, and X-ray-induced Cherenkov luminescence imaging system, etc.

[0003] Although online target area tracking and dose monitoring devices can be used independently, some devices have dual functions. For example, X-ray electronic portal imaging system, megavolt CBCT, ionizing radiation-induced acoustic imaging system, and X-ray-induced Cherenkov luminescence imaging system can not only reduce the occupation of the treatment room space, save equipment installation and calibration time, but also improve the stability of radiotherapy equipment. Among them, the advantages of X-ray electronic portal imaging system, ionizing radiation-induced acoustic imaging system, and X-ray-induced Cherenkov luminescence imaging system compared with megavolt CBCT are that their radiotherapy and image guidance are homologous, avoiding patients and medical staff from being exposed to additional imaging radiation sources, preventing the cumulative imaging dose caused by multi-fraction radiotherapy from exceeding 5% of the radiotherapy plan dose requirement, and being more in line with the radiation protection safety concept. However, due to the limited penetration of Cherenkov light, X-ray-induced Cherenkov luminescence imaging may not be able to provide clear imaging of deep-seated tumors in the body, and the electronic portal imaging system and ionizing radiation-induced acoustic imaging have the limitation of low soft tissue resolution.

[0004] In recent years, as an emerging radiotherapy imaging method, pair-production tomography (P2T) imaging technology is expected to achieve high-contrast differentiation between tumors and normal tissues to realize online target area localization without increasing additional radiation exposure by measuring the pair-production effect generated by high-energy X-ray irradiation of human tissues. At the same time, it dynamically monitors the spatial distribution of real-time radiation dose to achieve dual-guided radiotherapy of the target area and dose. However, the currently proposed P2T imaging system has low clinical feasibility. Its design draws on the full-ring detector structure and ideal detector performance of the PET imaging system, making it difficult to avoid the influence of X-ray irradiation on detector units. In addition, the reconstruction technology currently used in P2T imaging does not fully consider the interference of physical factors on data acquisition (such as photon attenuation, scattering, and random events), resulting in a decrease in imaging resolution. Especially in radiotherapy, the real-time dynamic imaging requirement leads to a low amount of raw data that can be collected within a short time frame. In this low count rate situation, if physical factor correction is not performed, the reconstructed image is vulnerable to noise interference, affecting the imaging quality.

[0005] Therefore, in view of the deficiencies of the existing technology, it is very necessary to provide a dual-quarter-ring radiotherapy pair-production tomography imaging system and an image reconstruction method to overcome the deficiencies of the existing technology. Summary of the Invention

[0006] In order to solve the above P2T imaging technology problems, the object of the present invention is to provide a dual-quarter-ring P2T imaging system and an image reconstruction method considering physical factor correction to overcome the influence of high-energy X-ray sources on detectors and improve the quality of P2T reconstructed images.

[0007] The object of the present invention is achieved by the following technical measures.

[0008] Provide a radiotherapy pair-production tomography imaging system, which is provided with:

[0009] A linear accelerator head;

[0010] Two ring detectors, the two ring detectors are located in the same axial plane and are symmetrically arranged;

[0011] The linear accelerator head is placed at the notch of the double-ring detector to avoid direct X-ray irradiation of the detection unit; the ring detector is composed of detection modules arranged along a ring.

[0012] Further, in the above radiotherapy pair-production tomography imaging system, the two ring detectors have the same shape.

[0013] Preferably, in the above radiotherapy pair-production tomography imaging system, the ring detector is a quarter-ring or three-sixteenths-ring or three-eighths-ring structure.

[0014] Preferably, in the above-mentioned radiotherapy homologous electron pair tomography imaging system, the detection module is composed of a plurality of scintillation crystals, and the plurality of scintillation crystals are fixed on the inner wall of the ring and arranged axially.

[0015] Preferably, in the above-mentioned radiotherapy homologous electron pair tomography imaging system, the plurality of scintillation crystals are arranged in a matrix.

[0016] Preferably, in the above-mentioned radiotherapy homologous electron pair tomography imaging system, the ring detector is composed of 12 detection modules in the circumferential direction, and each detection module is composed of 3 groups of LSO (Lutetium Oxyorthosilicate) scintillation crystals with a size of 13x13 and 4x4 mm 2 , and a thickness of 2 cm, arranged axially.

[0017] Preferably, in the above-mentioned radiotherapy homologous electron pair tomography imaging system, the radius of the ring detector is 82.4 cm.

[0018] The present invention also provides a P2T image reconstruction method based on physical factor correction, which is collected by the above-mentioned radiotherapy homologous electron pair tomography imaging system, and includes the following steps:

[0019] (1) Use Monte Carlo simulation software to simulate the generation of a high-energy X pencil beam by a linear accelerator head;

[0020] (2) Use Monte Carlo simulation software to simulate a double-ring detector composed of an arrangement of scintillation crystals;

[0021] (3) Use Monte Carlo simulation software to construct human tissue phantoms with different densities;

[0022] (4) Use Monte Carlo simulation software to simulate the irradiation of the phantom by a high-energy X pencil beam, simulate the tracking of the positron emission generated by the electron pair effect in the phantom, and the positron annihilates with nearby electrons to generate a pair of 511 keV gamma photons moving in opposite directions. Define a gamma photon event detected by two detection units simultaneously within a very short time (usually less than 10 ns) as a coincidence event, and the response path between the two detection units as the Line of Response (LOR). Set the coincidence event time window between several nanoseconds and several hundred nanoseconds, and record the number of coincidence events;

[0023] (4) Perform physical factor correction on the collected coincidence events, including the following steps:

[0024] (4.1) By measuring the total path length of the gamma photon pair passing through the phantom tissue, and then combining the tissue density to calculate the attenuation correction coefficient, the formula is:

[0025] …… (1);

[0026] Wherein, e is the exponential function, u is the attenuation coefficient of the tissue passed through, and D is the total length of the attenuation path;

[0027] (4.2) By adding a delayed coincidence window when recording coincidence events, the coincidence events within the delayed coincidence window are used as an estimate of random coincidence events;

[0028] (4.3) Generate an attenuation map according to the density of the human tissue filled in the phantom, preliminarily reconstruct a P2T image based on the collected coincidence events, and use the attenuation map and the P2T image as the input of the Single Scatter Simulation (SSS) algorithm;

[0029] Calculate the single-scatter distribution, and then scale it to the total scatter distribution to obtain scatter coincidence events;

[0030] (4.4) According to the attenuation correction coefficient, the estimated random and scatter coincidence events, perform attenuation, random, and scatter corrections on the coincidence events on each ROI collected, and its formula is:

[0031] …… (2);

[0032] Wherein, pp is the number of coincidence events, r is the number of random coincidence events, s is the number of scatter coincidence events, ac is the attenuation correction coefficient, and ture is the number of coincidence events after correction;

[0033] (5) Reconstruct a P2T image representing the spatial distribution of the pair production effect from the corrected coincidence events, which includes the following steps:

[0034] (5.1) Segment and discretize the X pencil beam according to the width of the detection unit;

[0035] (5.2) Take a LOR (Line of Response), calculate its intersection with the X pencil beam, and superimpose the number of corrected coincidence events on this ROL within the segment where the intersection is located;

[0036] (5.3) Repeat operation (5.2) for all LORs;

[0037] (5.4) Statistically count the total number of coincidence events in each segment on the X pencil beam as the intensity value of the P2T image for this segment.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. A dual-ring P2T imaging system provided by the present invention integrates a medical linear accelerator and a scintillation crystal detector in the same axial plane, and the linear accelerator head is located at the notch of the detector ring, avoiding direct irradiation of high-energy X-rays on the detector and causing damage to the detector, and improving the clinical feasibility of the P2T imaging system.

[0040] 2. The present invention also proposes a P2T image reconstruction method combined with physical factor correction. This method is based on a dual-quarter-ring P2T imaging system, uses the Monte Carlo method to simulate the electron pair effect generated by high-energy X pencil beams irradiating human tissues and the detection unit to collect coincidence events formed by positron annihilation. Attenuation, random, and scatter corrections are performed on the coincidence events, and the P2T image is quickly reconstructed using the intersecting line method, avoiding the decrease in imaging resolution of the P2T image caused by physical factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described with reference to the accompanying drawings, but the content in the drawings does not constitute any limitation to the present invention.

[0042] Figure 1 It is a schematic structural diagram of the dual-quarter-ring radiotherapy homologous electron pair tomography imaging system of the present invention.

[0043] Figure 2 It is a schematic diagram of the P2T imaging reconstruction method of the dual-quarter-ring.

[0044] Figure 3 It is a P2T reconstruction image of simulating X pencil beam irradiation of tissues with different densities, where (a) is the reconstruction image without considering physical factor correction, and (b) is the reconstruction image considering physical factor correction.

[0045] In Figures 1 to 2 it includes:

[0046] a linear accelerator head 100,

[0047] a ring detector 200, and a detection module 210. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The present invention is further described in conjunction with the following embodiments.

[0049] Embodiment 1

[0050] A radiotherapy homologous electron pair tomography imaging system is provided with:

[0051] a linear accelerator head;

[0052] two ring detectors, the two ring detectors are located in the same axial plane and are symmetrically arranged;

[0053] The linear accelerator head is placed at the notch of the double-ring detector to avoid direct X-ray irradiation of the detection unit; the ring detector is composed of detection modules arranged along a ring.

[0054] In the radiotherapy homologous electron pair tomography imaging system, the shapes of the two ring detectors are the same, and the curvatures, widths, and lengths of the two ring detectors are the same, and they are assembled on the gantry to form a symmetric structure.

[0055] The ring detector is a quarter or three-sixteenths or three-eighths ring structure. The detection module is composed of multiple scintillation crystals, and the multiple scintillation crystals are fixed on the inner wall of the ring and arranged axially. The multiple scintillation crystals are arranged in a matrix.

[0056] This embodiment also provides a P2T image reconstruction method based on physical factor correction, which is collected by the above-mentioned radiotherapy homologous electron pair tomography imaging system, and includes the following steps.

[0057] (1) Use Monte Carlo simulation software to simulate the generation of a high-energy X-ray pencil beam by the linear accelerator head.

[0058] (2) Use Monte Carlo simulation software to simulate the double-ring detector composed of the arrangement of scintillation crystals.

[0059] (3) Use Monte Carlo simulation software to construct human tissue phantoms with different densities.

[0060] (4) Use Monte Carlo simulation software to simulate the irradiation of the phantom by the high-energy X-ray pencil beam, simulate and track the pair production effect in the phantom to emit positrons, and the positrons annihilate with nearby electrons to generate a pair of 511 keV gamma photons moving in opposite directions. Define the gamma photon event detected by two detection units simultaneously within a very short time (usually less than 10 ns) as a coincidence event, and the response path between the two detection units as the line of response (LOR). Set the coincidence event time window between a few nanoseconds and a few hundred nanoseconds, and record the number of coincidence events. It should be noted that the very short time is usually less than 10 ns, and the specific time value can be flexibly set according to actual needs.

[0061] (4) Perform physical factor correction on the collected coincidence events, including the following steps:

[0062] (4.1) By measuring the total path length of the gamma photon pair passing through the phantom tissue, and then combining the tissue density to calculate the attenuation correction coefficient, the formula is:

[0063] ……(1);

[0064] Among them, \(e\) is the exponential function, \(u\) is the attenuation coefficient of the penetrated tissue, and \(D\) is the total length of the attenuation path.

[0065] (4.2) By adding a delayed coincidence window when recording coincidence events, the coincidence events within the delayed coincidence window are used as an estimate of random coincidence events.

[0066] (4.3) Generate an attenuation map according to the density of the human tissue filled in the phantom, preliminarily reconstruct a P2T image based on the collected coincidence events, and use the attenuation map and the P2T image as inputs to the Single Scatter Simulation (SSS) algorithm;

[0067] Calculate the single-scatter distribution, and then scale it to the total scatter distribution to obtain scatter coincidence events.

[0068] It should be noted that the specific algorithms for single-scatter estimation and scaling are conventional algorithms and not the innovation points of the present invention, so they will not be elaborated here.

[0069] (4.4) According to the attenuation correction coefficient, the estimated random and scatter coincidence events, perform attenuation, random, and scatter corrections on the coincidence events on each ROI collected, and its formula is:

[0070] ……(2);

[0071] Among them, among them, pp is the number of coincidence events, r is the number of random coincidence events, s is the number of scatter coincidence events, ture is the number of coincidence events after correction.

[0072] (5) Reconstruct a P2T image representing the spatial distribution of pair production events from the corrected coincidence events, which includes the following steps:

[0073] (5.1) Segment and discretize the X pencil beam according to the width of the detection unit;

[0074] (5.2) Take a LOR (Line of Response), calculate its intersection with the X pencil beam, and superimpose the number of corrected coincidence events on this ROL within the segment where the intersection is located;

[0075] (5.3) Repeat operation (5.2) for all LORs;

[0076] (5.4) Statistically calculate the total number of coincidence events in each segment on the X pencil beam as the intensity value of the P2T image for this segment.

[0077] A dual-ring P2T imaging system provided in this embodiment integrates a medical linear accelerator and a scintillation crystal detector in the same axial plane, and the linear accelerator head is located at the notch of the detector ring, avoiding direct irradiation of the detector by high-energy X-rays and causing damage to the detector, and improving the clinical feasibility of the P2T imaging system.

[0078] A P2T image reconstruction method combined with physical factor correction proposed in this embodiment is based on a dual-ring P2T imaging system. Using the Monte Carlo method, it simulates the pair production effect of high-energy X pencil beams irradiating human tissues and the detection unit collecting the coincidence events formed by positron annihilation. Attenuation, random, and scatter corrections are performed on the coincidence events, and the P2T image is quickly reconstructed using the intersecting line method, avoiding the degradation of the imaging resolution of the P2T image due to physical factors.

[0079] Embodiment 2

[0080] This embodiment is described by taking a radiotherapy homologous positron emission tomography imaging system with a specific structure as an example.

[0081] As Figure 1 、 Figure 2 shown, this embodiment provides a dual-quarter-ring P2T imaging system, which includes two planes with an inner diameter of 82.4 cm and coincident central axes installed axially on a quickly rotatable slip ring gantry. The two planes arranged along the axis are commonly called axial planes in the industry. Among them, the axial plane installed near the gantry entrance is used for kilovolt-level CT imaging, which can perform patient positioning and treatment alignment. The second plane installed axially along the entrance is used for P2T imaging-guided radiotherapy. In this plane, a linear accelerator head 100 is placed between two arc-shaped quarter detectors to avoid direct irradiation of the detection unit by X-rays. Each detector is arc-shaped and consists of 12 detection modules 210 along the circumferential direction, and each detection module 210 consists of 3 groups of 13x13 LSO (Lutetium Oxyorthosilicate) scintillation crystals with a size of 4x4 mm 2 、and a thickness of 2 cm arranged. Each scintillation crystal constitutes a detection unit.

[0082] As Figure 2 shown, the P2T image reconstruction method considering physical factor correction provided in this embodiment includes the following steps:

[0083] (1) Use Monte Carlo simulation software to simulate the high-energy X pencil beam generated by the linear accelerator head 100 and the dual-quarter-ring detector 200 composed of the arrangement of scintillation crystals.

[0084] (2) Use Monte Carlo simulation software to construct human tissue phantoms with different densities, which include six phantoms with a size of 5x5x5 cm3 cubes are successively filled with fat, lymph, liver, air, spine and ribs with densities of 0.92 g / cm 3 , 1.03 g / cm 3 , 1.06 g / cm 3 , 1.29x10 -3 g / cm 3 , 1.42 g / cm 3 and 1.92 g / cm 3 . The six cubes are surrounded by a cuboid as the background area and filled with water.

[0085] (3) Use Monte Carlo simulation software to simulate the high-energy X pencil beam irradiating the phantom. Simulate and track the positrons emitted by the electron-positron pair production in the phantom. The positrons annihilate with nearby electrons to generate a pair of 511 keV gamma photons moving in opposite directions. Define the gamma photon event detected by two detection units simultaneously within a very short time as a coincidence event. The response path between the two detection units is the LOR. Set the coincidence event time window between several nanoseconds and several hundred nanoseconds, and record the number of coincidence events.

[0086] (4) Correct the collected coincidence events according to formulas (1) and (2), which includes attenuation correction, random event correction and scatter event correction.

[0087] (5) Reconstruct the P2T image representing the spatial distribution of the electron-positron pair production from the corrected coincidence events, which includes the following steps:

[0088] (5.1) Segment and discretize the X pencil beam according to the width of the detection unit, and the length of each segment is 2.05 mm. It should be noted that the width of the detection unit refers to the sum of the width of the scintillation crystal and the gap between adjacent scintillation crystals. In this embodiment, the LSO (Lutetium Oxyorthosilicate) scintillation crystal with a size of 4x4mm 2 is used. The gap between two adjacent scintillation crystals is 0.1 mm. Therefore, the width of the detection unit is 4.1 mm. Segment and discretize the X pencil beam, and the length of each segment is 2.05 mm.

[0089] (5.2) Take an LOR, calculate its intersection with the X pencil beam, and superimpose the number of corrected coincidence events on this ROL within the segment where the intersection is located.

[0090] (5.3) Repeat operation (5.2) for all LORs.

[0091] (5.4) Statistically calculate the total number of coincidence events in each segment of the X pencil beam as the intensity value of the P2T image of this segment.

[0092] Figure 3 They are P2T images reconstructed without considering physical factor correction and with considering physical factor correction respectively. As the tissue density of the phantom increases, the intensity value of the P2T image reconstructed after physical factor correction increases. Existing reconstruction techniques do not consider physical factor correction. By Figure 3 comparing the result of (b) with Figure 3 that of (a), it can be seen that in the reconstructed image with physical factor correction considered, the contrast of different tissues increases, which is more conducive to distinguishing different tissues. The method of this embodiment can improve the quality of P2T reconstructed images.

[0093] As shown in Table 1, the calculated mean local image intensities corresponding to different tissues are 0.45 for water, 0.39 for fat, 0.47 for lymph, 0.62 for liver, 0 for air, 1.26 for spine, and 1.93 for rib respectively, and the intensity mean contrasts of different tissues relative to water are -7.6% for fat, 2.2% for lymph, 16.2% for liver, -100% for air, 47.3% for spine, and 62.2% for rib. If physical factor correction is not considered, the calculated contrasts between fat and lymph are -2.0% and 1.3% respectively. Therefore, physical factor correction is beneficial to improving the contrast of P2T images. Since the densities of lymph and liver are similar, the contrast of the P2T image at the liver part obtained before correction in Table 1 is relatively large. After correction, the contrast result is more reasonable. It can be seen that the reconstructed result after correction is beneficial to distinguishing different tissues and can improve the quality of P2T reconstructed images.

[0094] Table 1 Relationship table of P2T image intensity and tissue density

[0095]

[0096] A double-ring P2T imaging system provided in this embodiment integrates a medical linear accelerator and a scintillation crystal detector in the same axial plane, and the linear accelerator head 100 is located at the notch of the detector ring, avoiding direct irradiation of high-energy X-rays on the detector and causing damage to the detector, and improving the clinical feasibility of the P2T imaging system.

[0097] The P2T image reconstruction method combined with physical factor correction in this embodiment is based on a double-quarter-ring P2T imaging system. Using the Monte Carlo method, it simulates the pair production effect generated by high-energy X pencil beams irradiating human tissues and the coincidence events formed by positron annihilation collected by the detection unit. Attenuation, random, and scattering corrections are performed on the coincidence events, and the P2T image is quickly reconstructed using the intersecting line method, avoiding the decrease in imaging resolution of the P2T image caused by physical factors and being able to improve the quality of P2T reconstructed images.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A P2T image reconstruction method based on physical factor correction, characterized in that: Acquisition is performed by a radiotherapy homologous electron pair tomography imaging system, including the following steps: (1) Use Monte Carlo simulation software to simulate a high-energy X pencil beam generated by a linear accelerator head; (2) Use Monte Carlo simulation software to simulate a double-ring detector composed of an array of scintillation crystals; (3) Use Monte Carlo simulation software to construct a human tissue phantom with different densities; (4) Use Monte Carlo simulation software to simulate the irradiation of the phantom by a high-energy X pencil beam, simulate the tracking of the positron emission generated by the electron pair effect in the phantom, and the positron annihilates with nearby electrons to generate a pair of 511 keV gamma photons moving in opposite directions. Define the gamma photon event detected simultaneously by two detection units within a very short time not greater than 10 ns as a coincidence event, and the response path between the two detection units as a coincidence response line. Set the coincidence event time window between a few nanoseconds and a few hundred nanoseconds, and record the number of coincidence events; (4) Perform physical factor correction on the acquired coincidence events, including the following steps: (4.1) By measuring the total path length of the gamma photon pair passing through the phantom tissue, and then combining the tissue density to calculate the attenuation correction coefficient, the formula is: ac = e uD ……(1); where ac is the attenuation correction coefficient, e is the exponential function, u is the attenuation coefficient of the tissue passed through, and D is the total attenuation path length; (4.2) By adding a delayed coincidence window when recording coincidence events, use the coincidence events within the delayed coincidence window as an estimate of random coincidence events; (4.3) Generate an attenuation map according to the human tissue density filled in the phantom, and preliminarily reconstruct a P2T image based on the acquired coincidence events. Use the attenuation map and the P2T image as inputs to the single-scattering simulation algorithm; Calculate the single-scattering distribution, and then scale it to the total scattering distribution to obtain the scattered coincidence events; (4.4) According to the attenuation correction coefficient, the estimated random and scattered coincidence events, perform attenuation, random, and scattering corrections on the coincidence events on each ROI acquired, and the formula is: ture = (pp - r - s)·ac......(2); where pp is the number of coincidence events, r is the number of random coincidence events, s is the number of scattered coincidence events, and ture is the number of coincidence events after correction; (5) Reconstruct a P2T image representing the spatial distribution of the electron pair effect from the corrected coincidence events.

2. The P2T image reconstruction method based on physical factor correction according to claim 1, wherein: Reconstruct a P2T image representing the spatial distribution of the electron pair effect from the corrected coincidence events, specifically including the following steps: (5.1) Discretize the X pencil beam in segments according to the width of the detection unit; (5.2) Take a coincidence response line, calculate the intersection point of this coincidence response line and the X pencil beam, and superimpose the number of corrected coincidence events on this coincidence response line within the segment where the intersection point is located; (5.3) Repeat operation (5.2) for all coincidence response lines; (5.4) Statistically calculate the total number of coincidence events in each segment on the X pencil beam as the intensity value of the P2T image for that segment.

3. The P2T image reconstruction method based on physical factor correction according to claim 1 or 2, characterized in that: The radiotherapy homologous electron pair tomography imaging system is provided with: A linear accelerator head; Two ring detectors, the two ring detectors are located in the same axial plane and are symmetrically arranged; The linear accelerator head is placed at the notch between two annular detectors; the annular detectors are composed of multiple detection modules arranged along a ring.

4. The P2T image reconstruction method based on physical factor correction according to claim 3, wherein: The two annular detectors have the same shape.

5. The P2T image reconstruction method based on physical factor correction according to claim 4, wherein: The annular detector is a quarter or three-sixteenths or three-eighths annular structure.

6. The P2T image reconstruction method based on physical factor correction according to claim 5, wherein: The detection module is composed of multiple scintillation crystals, and the multiple scintillation crystals are fixed on the inner wall of the ring and arranged axially.

7. The P2T image reconstruction method based on physical factor correction according to claim 6, characterized in that: The multiple scintillation crystals are arranged in a matrix.

8. The P2T image reconstruction method based on physical factor correction according to claim 7, wherein: The annular detector is composed of 12 detection modules along the circumferential direction, and each detection module is arranged axially by 3 groups of LSO scintillation crystals with a size of 13×13 and 4×4 mm 2 , and the thickness is 2 cm.

9. The P2T image reconstruction method based on physical factor correction according to claim 8, wherein: The radius of the annular detector is 82.4 cm.

Images